JPH06249095A - Method and equipment for inspecting functional capacity of tank ventilating device for car - Google Patents

Abstract

PURPOSE: To diagnose a tank-venting system as soon as possible. CONSTITUTION: In a tank-venting system, the quantity of the liquid in a tank 10 is measured, and the pulse-duty factor to open a tank-venting valve TEV according to the quantity of the liquid is obtained. Then, the tank-venting valve is opened at the determined pulse-duty factor, a shut-off valve AV is closed, and when the pressure reaches the specified negative value, the tank-venting valve is closed, the gradient of underpressure decay to be reduced in the tank is obtained, and the sealability of the system is judged thereby. Since the pulse- duty factor to open the tank-venting valve when the negative pressure is increased during the sealing test is related to the quantity of the liquid in the tank, and the pressure increase is prevented from being too rapid or too intense when the tank is full, and the inspection period when the tank is almost empty can be shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for performing tank ventilation diagnosis of a vehicle having a tank ventilation device.

In the following, numerous references will be made to the magnitude of the negative pressure of the tank venting device. In this case, the negative pressure being “large” means a negative pressure having a large absolute value. Therefore, when the absolute value of the actual negative pressure becomes larger than the absolute value of the threshold negative pressure, the actual negative pressure “exceeds” the threshold negative pressure.

[0003]

2. Description of the Related Art Publication DE-A-4132055 (PCT
/ DE-A-92 007 25) describes a tank venting diagnostic method and apparatus which uses a decreasing gradient to negative pressure of the tank venting apparatus. The tank ventilation device includes a tank having a tank pressure sensor, an adsorption filter having a ventilation pipe that is connected to the tank through a tank connecting pipe and can be closed by a shutoff valve, and a tank that is connected to the adsorption filter through a valve pipe. It is equipped with a ventilation valve. The shutoff valve is closed and the tank vent valve is opened to create a negative pressure. When the predetermined negative pressure is obtained, the tank vent valve is closed again.
This causes the negative pressure to decrease again, and relatively slowly, especially when the tank venting device is closed. However, the negative pressure decrease gradient is related not only to the tightness of the device but also to the liquid amount in the tank. However, this effect can be eliminated when the negative pressure increase gradient is also measured and both gradients are correlated. This is described in the application of P4203100.

In order to increase the negative pressure, in the conventional method, the tank vent valve is opened at a predetermined maximum duty ratio. This duty ratio is set so that the desired negative pressure is not reached even in a nearly full tank before the desired minimum period, which is selected according to the time detection of the other measured quantity, in particular the lean correction measured quantity. If the tank is relatively empty,
Due to the fixed duty ratio, the period for pumping the tank venting device to the desired negative pressure is quite long. This directly affects the duration required for the entire inspection sequence. However, extending this period is problematic. This is because the tank ventilation diagnosis based on the determination of the negative pressure decrease gradient provides reliable results only when the vehicle is in a predetermined operating state. Especially for that reason idling is preferred. Since the idling phase will typically be 2 to 30 seconds, the inspection period should not be too long due to the time required to reach the desired negative pressure. Here, in a tank having a capacity of 60 l and a duty ratio of 10%, 2.5 l
4h gasoline engine idling 5hPa
Note that it takes about 40 seconds to reach the desired negative pressure of.

[0005]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a tank ventilation diagnosis method and device which are constructed so that the diagnosis can be carried out as soon as possible.

[0006]

According to the present invention, this problem is solved by the constructions set forth in claims 1 and 7. That is, for this reason, the present invention provides a method for inspecting the functional ability of a tank venting device of a vehicle equipped with an internal combustion engine (17), the tank venting device comprising a tank pressure sensor (11) ( 10) and a tank via a tank connecting pipe (12), and a shutoff valve (AV)
Functionality of a tank venting device of a vehicle comprising an adsorption filter (13) having a ventilation pipe (14) closable by means of a tank, and a tank ventilation valve (TEV) coupled with the adsorption filter via a valve pipe (15) In the method and apparatus for inspecting a), a) Tank liquid amount inspection is performed to obtain the tank liquid amount, the duty ratio is determined based on the obtained tank liquid amount, and the tank ventilation is performed at the duty ratio in the subsequent sealing inspection. Open the valve, b) carry out at least the following steps: b1) open the tank vent valve at a determined duty ratio and close the shut-off valve, b2) a predetermined pressure-related condition is met. At this time, close the tank ventilation valve, b3) calculate the negative pressure decrease gradient of the negative pressure that decreases in the tank, and b4) judge the hermeticity of the device using the calculated negative pressure decrease gradient. Adopted the configuration.

[0007]

According to the present invention, when the tank is almost empty, a large amount of gas is sucked from the tank ventilation device through the tank ventilation valve until the desired negative pressure is reached than when the tank is almost full. It is based on the recognition that the pipe must be pumped out. In order to ensure that different periods of time for pumping different amounts of gas do not differ, when a large amount of gas has to be pumped out, it must be pumped at high speed. Therefore, in the present invention, the more empty the tank,
The duty ratio for opening the tank vent valve is selected to be large. That is, by some method, the liquid amount is first detected, the duty ratio is determined based on the liquid amount, and then the determined duty ratio is set in the initial stage of the sealing test so that a desired negative pressure is obtained. Used to drive the tank vent valve. As a result, the desired negative pressure is always obtained in a relatively short period. When this negative pressure is reached, the tank vent valve is closed and a negative pressure decrease gradient is determined. Then, only by this decreasing gradient, or P420310
0, in combination with a pressure-increasing gradient,
In that case, the pressure increase gradient is standardized with respect to the reference duty ratio, and diagnosis is performed.

When the tank does not have a tank liquid amount sensor, it is effective to carry out the method of claim 2. In this method, the tank venting device is "test" first.
Pumped out. It is then considered that the tank is relatively full when it reaches a certain negative pressure within a fairly short time, while it is considered to be nearly empty when the period is long.

In practice, for a tank filled with a predetermined tank liquid amount range, a duty ratio of a few, for example, 2/3 or more, a first duty ratio is 1 / For tanks that are 3 to 2/3 full, it is sufficient to provide the third duty ratio at the second duty ratio, and if only 1/3 is filled.

The device of the invention is preferably implemented using a programmable controller which is programmed to carry out the method of the invention.

In a preferred embodiment of the present invention, the tank liquid level check and the seal check are carried out only when the internal combustion engine is in a predetermined operating state. Also, if the idling stage in which the tank liquid level test is performed is not long enough for the sealing test immediately after, the sealing test is performed in one of the subsequent idling stages. Further, the sealing test is performed only when the conditions for the sealing test are obtained within a predetermined period after the completion of the tank liquid amount test.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings.

In particular, the tank venting device shown in FIG.
Tank 10 equipped with a differential pressure sensor 11, and tank connection pipe 1
A tank ventilation valve arranged in an adsorption filter 13 which is connected to the tank via 2 and which has a ventilation pipe 14 in which a shut-off valve AV is inserted, and a valve pipe 15 which connects the adsorption filter with an intake pipe 16 of an internal combustion engine 17. And TEV. The tank vent valve TEV and the shutoff valve AV are driven by the sequence controller 19. The tank vent valve TEV can also be driven according to the operating conditions of the engine 17, independent of the diagnostic process described here, which is typically performed only once per driving cycle. The catalyst 20 is arranged in the exhaust gas passage 30 of the engine 17, and the oxygen sensor 21 is arranged in front of the catalyst 20. The oxygen sensor outputs the signal to the lambda closed loop controller 22, which determines the operating signal for the injector 23 of the intake pipe 16 based on the signal.

The determination of whether the tank venting system is functional is made using the slope calculator 24 and the determiner 18. Furthermore, a time measuring device 25 is provided. Between the gradient calculator 24 and the sequence controller 19, the duty ratio /
The gradient characteristic line 30 and the waiting time / gradient characteristic line 31 are connected.

When the idling signal generator 27, which cooperates with the throttle valve 26 of the engine, indicates idling, the sequence controller 19 starts a sequence for checking the functional capability of the tank venting device. Furthermore, it may be provided that the drive signal generator indicates that the associated vehicle is stationary or traveling slowly.
Checking for this condition is illustrated by step s2.1 in FIG. If this condition is fulfilled, a tank fluid quantity test, which will be described in more detail below with reference to FIGS.

Subsequent to the tank liquid amount inspection, an inspection regarding the functional capability of the tank ventilation device is performed. However, this inspection is not performed until step s2.7. This is because various conditions must be investigated before that. First, it should be noted that the tank must be re-dominated by normal pressure, especially when not only the negative pressure decreasing gradient but also the increasing gradient is used for diagnosis. Therefore, in step s2.3, the waiting time t_W elapses. The emptyer the tank,
The time from the predetermined negative pressure to the normal pressure again becomes long. Therefore, this waiting time is related to the liquid volume, which is taken into consideration by the waiting time / gradient characteristic line 31.

Furthermore, it should be noted that in some cases, the condition of the sealing test does not immediately follow the tank liquid amount test. That is, at step s2.3, the end time T_
End is measured. In step s2.4, it is checked whether it is idling. If so, the relevant time point T is measured in step s2.5. The delay period t_VERZUG is calculated as the difference between T and T_End. If this delay period is shorter than a predetermined period, eg 2 minutes, as examined in step s2.6, the above mentioned sealing test step s2.7 is reached. When that ends, the entire process ends.

It should be pointed out here that, if a tank liquid quantity sensor is provided, the number of processing steps in FIG. 2 can be considerably reduced to obtain the same result. In that case, the liquid volume is simply measured (this is performed in the tank liquid volume inspection in step s2.2 in the sequence of FIG. 2), and the liquid volume is used for tank ventilation during the sealing inspection. The duty ratio for driving the valve is determined and then a seal check is performed. However, in the following, it is assumed that such a liquid amount sensor does not exist.

Next, a tank liquid amount inspection sequence according to this embodiment will be described with reference to FIGS. 3 and 4.

Step s3. Of the sequence shown in FIG.
At 1, the correction factor FR1 output from the lambda closed loop controller is measured at a representative time. In the illustration of FIG. 4A, this is the end point of the p (proportional) change from the lean to the rich direction. Simultaneously with this measurement, the tank ventilation valve is opened at a predetermined duty ratio (step s3.
2). This opening is rapidly performed with a predetermined duty ratio, but this duty ratio must not be too large and must not exceed, for example, 10%. This is because almost pure fuel vapor is drawn in from the tank venting device, which causes the mixture to become rich and the engine to stop.
Therefore, in this embodiment, the tank vent valve is opened only slowly, as shown in FIG. Regarding the time scales of FIGS. 4 and 6, it should be mentioned that the lambda control oscillation during idling is typically about 4 seconds. Comparing FIGS. 4 (a) and 4 (b), it can be seen that the tank vent valve is controlled to be opened to a duty ratio of 50% within about 10 seconds.

The opening control up to the above-mentioned large value is performed only when the lambda closed loop control device 22 has not previously indicated the fuel-rich gas from the tank ventilation device due to the strong lean correction. This is step s3.3
And s3.4. In step s3.3, the control factor FR is measured when the same conditions as before, ie here the end of the p change from lean to rich, are fulfilled.
This measured value is FR2. The difference between FR1 and FR2 is ΔF
It becomes R. In step s3.4, it is checked whether ΔFR is larger than the threshold ΔFR_TH. If so, the entire inspection process ends. This is for two reasons. One is that when the fuel evaporation is strong, the pressure gradient measurement, which gives a concrete image of the tightness of the tank ventilation device, becomes unreliable. The second reason is that when a large amount of fuel is inhaled from the tank vent, it must be scavenged, which is not possible during the inspection process.

When the fuel is not sucked from the tank ventilation device or is very small and there is no risk of a failure in the subsequent inspection, the shutoff valve AV is closed in step s3.5. In that case, the negative pressure Δ associated with the relevant period T1
p1 is measured. Continuously repeated negative pressure measurement in steps s3.6 and s3.7 (step s3.
By comparing 6) with the predetermined negative pressure Δp_FIX of the measured negative pressure (step s3.7), it is checked whether the predetermined negative pressure has already been reached. In this example, this is 5 hPa. When this predetermined negative pressure is reached, the tank vent valve TEV is closed and the shutoff valve AV is opened in step s3.8.
Further in step s3.9 the relevant time period T2 is measured and the time period Δt = T2-T1 is calculated. The negative pressure increase gradient Δp_GRAD is obtained as Δp_FIX / Δt. This is not the case in the present example, but if this gradient is used in a subsequent sealing test, it is simply a value Δp as a pressure change.
It is recommended to use the value Δp_FIX−Δp1 instead of _FIX.

FIG. 4 (d) shows two curves for increasing the negative pressure. The solid line relates to the negative pressure when the tank is half full, while the dotted line shows the negative pressure gradient when the tank is almost empty. In this manner, the negative pressure gradient calculated in step s3.9 can roughly determine whether the tank is almost empty, almost half filled, or almost full. Since it has already been confirmed in step s3.4 that there is no or almost no vaporization or vaporization of the fuel, the vaporized fuel will not cause this determination to be false.

As described above, the negative pressure increase gradient is used to obtain the duty ratio τ_TEV of the tank ventilation valve used during the waiting time t_W and the subsequent sealing test. This is done using characteristic lines 30 and 31 in step s3.10.

Next, referring to FIGS. 5 and 6, step s
The sealing test of 2.7 will be described in detail.

Steps s5.1 to s5.4 of the sequence of FIG. 5 are functionally identical to steps s3.1 to s3.4. As can be seen from FIGS. 6 (a) and 6 (b), only the values FR3 and FR4 are measured for the control coefficient instead of the values FR1 and FR2 when the tank vent valve is controlled to open slowly. If it is found that a fairly strong lean correction is required during the opening control of the tank ventilation valve, the inspection process is interrupted in step s5.4. Otherwise, step s5.5 follows, where shutoff valve A
V is closed and then steps s3.6 to s above
In steps s5.6 and s5.7 corresponding to 3.7, it is checked whether the negative pressure Δp_FIX has already been reached. If so, the tank vent valve is closed in step s5.8. This is time T5 (FIG. 6).

From now on, the negative pressure of the tank is slowly reduced.
In step s5.9, the negative pressure decrease gradient is obtained.
This is simply done by determining the negative pressure reduction within the predetermined period or the period required for the predetermined pressure reduction and dividing the negative pressure reduction by the period. In step s5.10 it is checked whether this negative pressure decrease gradient is greater than the threshold value TH.
If so, an instruction that the device is not sealed is output in step s5.11. After this step or after step s5.10, the following step s5.12 is reached, where the shut-off valve AV is opened again.

As can be seen from FIGS. 6 (b) to 6 (d),
The time course of a half-filled tank (solid line) and the time course of an almost empty tank (dotted line) are different. In the case of a half-filled tank, the duty ratio of 25% obtained in step s3.10 is reached at time T4, and then remains unchanged.
The shutoff valve is closed. In the case of an almost empty tank, the duty ratio τ_TEV of 50% is set in step s3.10 and reaches this after T4 ′. In this case as well, the shutoff valve is closed again and the duty ratio remains unchanged. In both cases, the specified negative pressure Δp_
The period until reaching FIX is almost equal. For a half-filled tank, there will be a period T5-T4, while for an almost empty tank there will be a period T5'-T4 '. In the case of a nearly full tank, a duty ratio of 12.5% is set, for example.

As mentioned at the beginning, the duty ratio of a full tank is always used in the past. As a result,
When the tank is almost empty, the period that elapses until the negative pressure Δp_FIX of the tank is reached is considerably longer than T5′-T4 ′ in FIG.

Since the duty ratio for opening the tank vent valve when increasing the negative pressure at the time of sealing inspection is related to the tank liquid amount, it is possible to prevent the pressure from increasing too fast or too strong when the tank is full. As well as
The inspection period can be shortened when the tank is almost empty. This is because the tank vent valve is driven with a considerably large duty ratio, which makes it possible to quickly increase the negative pressure in spite of the large volume to be exhausted.

In the sequence of FIG. 5, step s5.
Although the sealing test of 10 is performed only by the negative pressure decrease gradient, the specific sealing determination method is not so important in the present invention, and the essential thing is to use a method capable of increasing the negative pressure. That is, this negative pressure increase is performed at the open duty ratio of the tank ventilation valve related to the tank liquid amount.

Furthermore, it should be noted that the principles of the present invention are not limited to seal inspection. For example, P4
As described in 132055 or P4203100, the negative pressure increasing gradient or the negative pressure decreasing gradient can also be used to detect clogging of the tank venting device. Such tests can be performed in addition to the tests described in this example. Importantly, the desired negative pressure is adjusted using the tank vent valve duty ratio which is dependent on the tank fluid level.

[0033]

As described above, according to the present invention, the duty ratio for opening the tank vent valve when increasing the negative pressure during the sealing test is related to the tank liquid amount, so that the pressure increase when the tank is full is increased. Is prevented from being too fast or too strong, and the inspection period can be shortened when the tank is almost empty.

[Brief description of drawings]

FIG. 1 is a block diagram schematically illustrating the configuration of a tank ventilation diagnostic device of the present invention.

FIG. 2 is a flowchart illustrating a diagnostic method of the present invention.

FIG. 3 is a flowchart illustrating the flow of tank liquid amount inspection in the flowchart of FIG.

FIG. 4 is a signal waveform diagram with respect to time illustrating the sequence of FIG.

5 is a flow chart diagram for explaining the flow of the seal inspection in the flow chart of FIG.

6 is a signal waveform diagram with respect to time illustrating the sequence of FIG.

[Explanation of symbols]

 10 Tank 11 Tank Pressure Sensor 13 Adsorption Filter 15 Tank Ventilation Valve 17 Engine 18 Judgment Device 19 Sequence Control Device 20 Catalyst 22 Lambda Control Device 24 Gradient Calculation Device

 ─────────────────────────────────────────────────── ———————————————————————————————————————————————————————————————————————————————————————————

Claims (7)

[Claims] 1. A method for inspecting the functional capability of a tank venting device of a vehicle equipped with an internal combustion engine (17), the tank venting device comprising a tank (10) provided with a tank pressure sensor (11), A ventilation pipe (1) that is connected to the tank via a connecting pipe (12) and can be closed by a shutoff valve (AV).
An adsorption filter (13) having a valve pipe (1)
5) In a method for inspecting the functional ability of a tank venting device of a vehicle equipped with a tank venting valve (TEV) which is connected to an adsorption filter via: The duty ratio is determined on the basis of the obtained tank liquid amount, and the tank ventilation valve is opened at the duty ratio in the subsequent sealing inspection. B) At least the following steps of the sealing inspection, that is, b1) Open at the determined duty ratio and close the shut-off valve, b2) close the tank vent valve when certain pressure related conditions are met, b3) create a negative pressure decrease gradient of the negative pressure decreasing in the tank. B4) A method for inspecting the functional capability of a tank venting device of a vehicle, characterized in that the airtightness of the device is judged using the negative pressure decrease gradient thus found. 2. The step (a) comprises the following steps: a1) opening the tank vent valve at a predetermined duty ratio and closing the shutoff valve, and a2) a negative pressure increase gradient of negative pressure increasing in the tank. And a3) determining the duty ratio based on the obtained negative pressure increase gradient, and opening the tank vent valve at the duty ratio in the subsequent sealing test. . 3. The process according to claim 2, wherein a lean correction inspection is performed in the step (a1) or (b1), and the process is interrupted when the obtained lean correction exceeds a predetermined threshold value. Method. 4. The method according to claim 2, wherein the tank liquid level check and the seal check are performed only when the internal combustion engine is in a predetermined operating state. 5. The sealing test is carried out in one of the subsequent idling stages when the idling stage in which the tank liquid level test is performed is not long enough for the sealing test immediately after. Method according to any one of claims 1 to 4. 6. The method according to claim 4, wherein the sealing inspection is performed only when the conditions for the sealing inspection are obtained within a predetermined period after the tank liquid amount inspection is completed. 7. A device for inspecting the functional capability of a tank venting device of a vehicle equipped with an internal combustion engine (17), the tank venting device comprising a tank (10) provided with a tank pressure sensor (11), A ventilation pipe (1) that is connected to the tank via a connecting pipe (12) and can be closed by a shutoff valve (AV).
An adsorption filter (13) having a valve pipe (1)
5) A tank vent valve (TEV) coupled to the adsorption filter via 5), a time measuring device (25), and a gradient for calculating a negative pressure change gradient using signals from the tank pressure sensor and the time measuring device. A calculator (24), a judgment device (18) for judging the functional capability of the tank ventilation device based on a signal from the gradient calculation device, and a tank ventilation valve and a shutoff valve opening / closing so that the negative pressure change gradient can be detected. Sequence control device for time control (1
9) and a device for inspecting the functional capability of a tank venting device of a vehicle, which has the following sequence control device performs the following sequence, that is, a) tank liquid amount inspection to obtain and obtain the tank liquid amount. The duty ratio is determined on the basis of the tank liquid amount obtained, and the tank ventilation valve is opened at the duty ratio in the subsequent sealing inspection, b) the sealing inspection is performed in the following steps, that is, b1) the tank ventilation valve is determined in duty. Open at a ratio and close the shutoff valve, b2) close a tank vent valve when a predetermined pressure-related condition is met, b3) find a negative pressure decrease gradient of the negative pressure decreasing in the tank, b4) The functional capability of the tank venting device of the vehicle, which is configured to judge the hermeticity of the device using the obtained negative pressure decrease gradient, to perform by the process, and to perform the sequence. Device to inspect.